1. Field of the invention
The present invention is related to a new method for producing ML-236B, a precursor of pravastatin sodium, in particular to a method for producing ML-236B lactone form(I), free acid form (II), and sodium salt(III) shown in the following formulae by using a new microorganism isolated from soil. ML-236B is obtained from the culture broth of this microorganism and it is used as a substrate of pravastatin sodium which is a potent cholesterol-lowering agent used in treatment for hypercholesterolemia. ##STR1##
2. Description of the Prior Art
It has been known that heart disease such as myocardial infarction, arteriosclerosis have been caused mainly by hyperlipidemia, especially hypercholesterolemia. It was reported by U.S. Pat. No. 3,983,140 and UK. Patent No. 1,453,425 that a cholesterol-lowering compound called ML-236B produced by a fungus Penicillium sp. had been discovered. ML-236B is produced by soil microorganisms or chemical conversion. It was reported that Penicillium brevicompactin, Penicilmyces sp., Trichoderma longibraiatum, Trichoderma pseudokoningi, Hyphomyces chrisopomus and Penicillium citrium produced ML-236B(David et al., "Biotechnology of filamentous fungi", p241; JP Publication No. Pyung 4-349034).
Particularly, Sankyo Pharmaceutical Company, Japan, had developed Penicillium citrium SANK 18767 by mutation of a strain Penicillium citrium NRRL-8082 which was reported in 1971. By continuing strain development for 14 years, they had obtained Penicillium citrium Thom SANK 13380. ML-236B productivity had risen from 1.75 mg/l to 42.5 mg/l.
However, the method above described required so much time about 14 years to develop a strain with high ML-236B productivity. It also needed a little long cultivation time, 14 days, and showed relatively low ML-236B productivity.